Potentiometer assembly



March 1956 c. H. JORGENSEN ET AL 2,738,405

POTENTIOMETER ASSEMBLY 2 Sheets-Sheet 1 Filed Jan. 17, 1955 rgensen BY Harry G. Zelsloff INVENTORS Clarence H. do

The/r Affqrney c. H. JORGENSEN ETAL 2,738,405

March 13, 1956 I POTENTIQMETER ASSEMBLY 2 SheetsSheet 2 Fild Jan, .17, 1955 INVENTORS Clarence H. Jorgensen By Harry C. Zeis/off 6149 1/. mm Their Attorney United States Patent POTENTIOMETER ASSEMBLY Clarence H. Jorgensen, East Rochester, and Harry C. Zeisloft, Rochester, N. 'Y., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application January 17, 1955, Serial'No. 482,201

Claims. (Cl. 201-48) This invention pertains to potentiometers, and particularlyto a double potentiometer assembly.

The diffieulties involved in winding wire resistors having the same number of turns and the same spacing between turns so that equal lengths thereof willhave the same ohmic resistaucaiswell recognized by those skilled in the art. inasmuch as production of wire wound resistors of exactly the same characteristics, i. e. linearity and ohmic resistance, is not feasible, some compensating means must be incorporated in a device which includes two such resistors. This invention relates to a double potentiometer assembly wherein the diiference in ohmic resistance and linearity between piek-up points on both otentiometers is maintained at a minimum. Accordingly, among our objects are the provision of a double po tentiometer assembly including means to compensate for the inherent differences in the ohmic value-of two resistors so as to minimize the ohmic dificrences therebetween throughout the range of operation of the assembly; the further provision of a double potentiometer assembly comprising two arcuate resistors including means for varying the shape, or configuration, of one resistorso as to compensate for differences in the linearity -there'oetween; and the still further provision of a double potentiometer assembly including a pair of wipers and means for effecting relative movement between the wipers to establish starting'pick-up point for the potentiometors.

The aforementioned and other objects are accomplished in the present invention by supporting the wipers and the resistors for movement relative to each other. Specifically, the double potentiometer assembly includes a stationary housing having a cup-like bottom portion formed with oppositely extending, centrally located tubular sections within which bearing means are disposed for rotatably supporting an operating shaft. The housing also includes a cup-shaped cap arranged to be secured to the bottom of the housing so as to close the chamber formed therebetween. The inwardly extending tubular section of the housing bottom portion supports a generally circular fixed resistor base having an arcuate groove therein. The arcuate groove in the fixed resistor base subtends an angle slightly less than 180, and has secured therein a wire wound resistor. A portion of the fixed resistor base rotatably supports a movable resistor base having a toothed peripheral portion engageable by a pinion supportsu in the bottom portion of the housing. The pinion is accessible from the exterior of the housing and may be manually rotated to vary the position of the movable resistor base with respect to the fixed resistor base.

The movable resistor base is formed with a groove, subtending 360. A portion of this groove subtending an angle of 180 is concentric with the groove in the fixed resistor The remaining portion of the groove in the movable resistor base extends along a helical path ina radially outward direction. A second wire wound resistor is secured to a guide member having a tongue portion received in the groove of the movable resistor base.

Accordingly, by rotating the movable resistor base, the shape, or configuration of the resistor carried by the guide may be altered. More particularly, by rotating the movable resistor base, the resistor carried by the guide can be fanned to vary its resistive characteristics with respect to the fixed resistor.

The operating shaft receives a hub which supports a pair of wiper carriers. The wiper carriers are piloted on the hub and connected to rotate with the shaft. Portions of the two wiper carriers are superimposed, the upper carrier having formed therein a screw threaded opening within which a screw having an eccentric pin is'supported. The eccentric pin isrecived in a. slot in the lower wiper carrier whereby the carriers may be moved relative to each other byrotation of'the screw. Each carrier supports a pair of wipers, one of which contacts its respective resistor elements, and the other of wl ich contacts its respective portion of a split pick-up ring supported by the fixed resistor base.

Each end therein of both resistors is connected to a conductor, and each portion of the split pick-up ring is also connected to a conductor. The wiper carriers are initially adjusted relative to each other so that at the starting point, both resistor'contacting wipers contact the first turn of their respective'resistors whereby the resistance'betweu the ends ofbcth resistors and their wipersis zero. The potentiometer assembly is designed so that the incrcrnentsof resistaucepie'ked up by both wipers from the two resistor elements will be substantially the same throughout the full range of operation. liioreover, the resistance varies inasubstantiallylinear relationship with rotati nal the shaft and'the wipers. in order to obtain equal resmtan e increments from both re throughout the full range of operation, the movable resistor base is adjusted to'vary the'configw tion of the re sistor which is secured'to'the guide'that rides in the groove of the movable resistor base. Thereafter, the adjusting pinion may be securely held in place by any suitable means.

Further objects audadvantagcs of the present invention will be apparent from the following description, ref:- erence being'had to the accompanying drawings wherein a preferred embodiment of the present invention-is clearly shown.

In the drawings:

Fig. l is a side view, in elevation, of a dcuble potentiometer assembly constructed according to this invention.

Fig. 2 is enlarged view, taken in the direction of arrow 2 in Fig. '1 with the cap removed.

Fig. 3 is a view, partly in section and partly in elevation, taken along line 3-3 of Fig. '2.

Fig. 4 is a view, partly in section and partly inelevation, taken along line 44 of Fig. 3.

Fig. 5 is an exploded view illustrating the wiper assembly.

Fig. 6 is a top view, in elevation, of the movable resistor base.

With particular reference to Figs. 1 through 3, the double potentiometer assembly is-disposed Within a housing generally depicted by the numeral 10, the housing including a generally cup-shaped bottom portion 11 and a cap portion 12 having threaded engagement. The bottom portion 11 is formed with centrally located, opposite'ly extending tubular sections 13 and 14. A ball hearing assembly 15 has its outer race supported in the tubular section 13, and shall bearingassembly 16 has its outer race supported in the tubular section 14. The inner races of the ball bearing assemblies 15 and 16 are maintained in spaced relation by a sleeve 17. The ball bearing assemblies 15 and 16 ro't'atably support an operating shaft 18 having 'a longitudinally splined spindle 19 3 formed on the outer end thereof. The spindle 19 may be connected to any suitable device, not shown, for imparting rotation to the shaft. The inner end of the shaft 18 receives a hub 20, the purpose of which will be described hereinafter.

The tubular section 13 of the housing supports a fixed resistor base 21. As seen paritcularly in Figs. 2 through 5, the fixed resistor base is formed with arcuate portions 22 and 23 of difierent radii. Portion 22 is of larger radii than portion 23 and subtends an angle of less than 180. Portion 22 is formed with an arcuate grove 24, which is concentric with the shaft 18. A wire wound resistor 25 is securely fastened in groove 24, one end of the resistor 25 being connected to a conductor 26 and the other end of the resistor25 being connected to a conductor 27. The portion 22 is also formed with a radially extending groove 28 which intersects an annular groove 29 that is also concentric with the shaft 18. A split pick-up ring assembly including arcuate portions 36 and 31 is securely fastened in the groove 29. Arcuate section 31 is connected to a conductor 33, which extends through the slot 28, while arcuate section is connected to a conductor 32, which, likewise, extends through a radial slot in the fixed resistor base 21.

The fixed resistor base 21 is also formed with an annular shoulder 34, which abuts the bottom portion 11 of the housing. A movable resistor base 35 is rotatably supported about the annular shoulder 34, the movable resistor base 35 being formed with a toothed peripheral portion 36. The toothed peripheral portion 36 engages a pinion gear 37, which is rotatably supported in the bot tom portion 11 of the housing. As seen in Fig. 3, the pinion 37 is formed with an exteriorly accessible slot 38 arranged to receive a tool for imparting rotation to the pinion 37 and the movable resistor base 35. As seen particularly in Fig. 6, the movable resistor base 35 is formed with a groove 39, which subtends an angle of 360. The ends 40 and 41 of the groove 39 are radially spaced, as depicted in Fig. 6. Actually 180 of the groove 39 from the end 40 in a counterclockwise direction, as viewed in Fig. 6, are concentric with the shaft 18. The

to by means of screws 64 and 65, respectively. The wiper 62 isarranged to contact annular segment 31 of the ring assembly while the wiper 62 is arranged to contact resistor 25. The carriers 51 and 52 are connected to rotate with the shaft 18 by means of a nut 66, which engages a threaded end portion 67' of the shaft. A washer 68 is interposed between the nut 66 and the upper carrier 51. By rotating the screw 60, it may be seen that carriers 51 and 52 may be positioned angularly relative to each other. In this manner, the wipers 56 and 63 may be positioned so that they contact the first turn of their respective resistors 25 and 42 at a predetermined angular position of the shaft 18.

As alluded to hereinbefore, it is practically impossible to wind two wire resistors having identical ohmic values for equal increments of length, and also having the same linear resistance characteristics. Accordingly, in the present potentiometer assembly, the configuration of resistor 42 may be altered by imparting rotation to the removable resistor base 35 through the pinion 37. By rotating the base 35, the shape of the resistor 42 can be varied so that it is concentric with the shaft 18 or entirely eccentric with respect to the shaft 18. In other words, during clockwise movement of the base 35, as viewed in Figs. 2, 4 and 5, the end 70 of the resistor 42 may be moved in a radially outward direction. In this manner, both the ohmic value of an increment of resistor 42, as picked up by wiper 56, and the linearity of the resistor may be varied so as to render its characteristics in substantial conformity with that of resistor 25. Thus, the pinion 37 is adjusted until the ohmic values picked off points along resistors 25 and 42 during moveremaining 180 of the groove 39 extend in an outward helical path. An annular guide member 42 is disposed within the groove 39. As depicted in Figs. 2 and 5, the annular guide member 42 is formed with a plurality of circumferentially spaced, upstanding fingers 43, which are secured to opposite sides of a second wire wound resistor 44.

One end of the wire wound resistor 44 is connected to a conductor 45, while the other end of the resistor 44 is connected to a conductor 46. The conductors 26, 27, 28, 32, 45 and 46 extend through an opening in the housing 11 within which a conduit 47 for enclosing the conductors is secured.

With reference to Figs. 2, 3 and 5, it may be seen that the hub 20 is formed with a stepped bore and is slidably received on the stepped end of shaft 18. The hub 20 also includes a reduced diameter portion 50, which receives a pair of superimposed wiper carriers 51 and 52. The lower wiper carrier 52 is formed with an opening 53, which receives the smaller diameter portion of the hub 20, and a slot 54. The carrier 52 supports a pair of wipers or contacts 55and 56, which are fixedly attached thereto by means of screws 57 and 58, respectively. The wiper 55 engages the annular segment 30 of the contact ring assembly, while the wiper 56 is arranged to contact the resistor 42. Similarly the carrier 51 is formed with a 'circular opening 59, which receives the smaller diameter portion 50 of the hub. In addition, the carrier 51 is formed with a threaded opening that receives a screw 60 having an eccentric pin 61 extending axially thereof. The pin 61 is received in the slot 54 of the carrier 52, the purpose of which will be described hereinafter. The carrier51 also supports a ment of the shaft 18 throughout its entire range on resistor 42 are substantially equal to those picked off resistor 25. After this adjustment has been made, the pinion 37 is locked in place by any suitable means, such as sealing wax. Similarly, after the starting pick-up point of zero resistance on resistors 42 and 25 has been es tablished by adjustment of screw 60, the screw 60 is locked in place by any suitable means, such as sealing wax.

From the aforegoing, it is apparent that the present invention provides unique means for altering the resistive characteristics of one resistor so as to match the characteristics of a second resistor. Furthermore, by virtue of this construction, a double potentiometer unit in which both potentiometers have the same resistance characteristics and, therefore, the same output characteristics, may be manufactured.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A double potentiometer assembly comprising, a housing, an operating shaft rotatably supported in said housing, a first wire wound resistor, means disposed in said housing and fixedly supporting said first resistor so that it describes an arc concentric with said shaft, a second wire Wound resistor, a rotatable member disposed in said housing and having a surface with merging portions concentric and eccentric with respect to said shaft, means supporting said second resistor and engaging part of the surface of said rotatable member whereby the configuration of said second resistor corresponds to said part of said surface, wiper means carried by said shaft and engageable with said resistors, and means to rotate said member so as to vary the configuration of said second resistor whereby the resistance characteristics of said second resistor can be matched with the resistance characteristics of said first resistor.

2. A double potentiometer assembly comprising, a

housing, an operating shaft rotatable supported in said housing, a first wire wound resistor, means fixedly supporting said first resistor so that it describes an arc concentric with said shaft, a second wire wound resistor, a rotatable member disposed in said housing having a groove with merging portions concentric and eccentric with respect to said shaft, means supporting said second resistor and engaging part of said groove whereby the configuration of said second resistor corresponds to said part of the groove, wiper means carried by said shaft and engageable with said resistors, and means to rotate said member so as to vary the configuration of said second resistor whereby the resistance characteristics of said second resistor may be matched with the resistance characteristics of said first resistor.

3. A double potentiometer assembly comprising, a housing, an operating shaft rotatably supported in said housing, a first wire wound resistor, means fixedly supporting said first resistor so that it describes an arc concentric with said shaft, a second wire wound resistor, a rotatable member disposed in said housing having a groove with merging portions concentric and eccentric with respect to said shaft, a guide having a plurality of spaced fingers supporting said second resistor and a tongue portion disposed in part of said groove whereby the configuration of said second resistor corresponds to said part of the groove, wiper means carried by said shaft and engageable with said resistors, and means to rotate said member so as to vary the configuration of said second resistor whereby the resistance characteristics of said second resistor may be matched with the resistance characteristics of said first resistor.

4. A double potentiometer assembly comprising, a housing, an operating shaft rotatably supported in said housing, a first wire wound resistor, a member fixedly supported in said housing and having an arcuate groove concentric with said shaft, said first resistor being secured in said arcuate groove, a second wire wound resistor, a rotatable member disposed in said housing and having a groove with merging portions concentric and eccentric with respect to said shaft, means supporting said second resistor and engaging part of said groove whereby the configuration of said second resistor corresponds to said part of the groove, means connected with said rotatable member for efiecting movement thereof so as to vary the configuration of said second resistor whereby the resis tance characteristics of said second resistor can be matched with the resistance characteristics of said first resistor, a pair of carriers attached to said shaft, each carrier supporting a wiper arranged to contact one of said resistors, and means for effecting relative angular movement between said carriers so as to establish a starting pick-up point of zero resistance on each resistor after said resistance characteristics of the resistors have been matched.

5. The combination set forth in claim 4 wherein one of said carriers has a threaded opening and the other of said carriers has a slot, said carriers being superimposed so that said threaded opening is in alignment with said slot, and wherein the means for efiFecting angular movement between said carriers comprises a screw engaging the threaded opening in said one carrier and having an eccentric pin disposed in the slot of said other carrier.

6. A double potentiometer assembly comprising, a housing, an operating shaft rotatably supported in said housing, a first wire wound resistor, a fixed member supported in said housing and having an arcuate groove concentric with said shaft within said first resistor is fixedly secured, said groove and said first resistor subtending an are less than 21 second Wire wound resistor, a member rotatably supported in said housing and having a groove subtending an angle of 360 with portions of said groove being concentric and eccentric with respect to said shaft, a guide element secured to said second resistor and having engagement with part of the groove in said rotatable member whereby the configuration of said second resistor corresponds to said part of the groove in said rotatable member, wiper means carried by said shaft and engageable with said resistors, and means connected with said rotatable member for imparting movement thereto so as to vary the configuration of said second resistor whereby the resistance characteristics of said second resistor may be matched with the resistance characteristics of said first resistor.

7. The combination set forth in claim 6 wherein said rotatable member is formed with a toothed peripheral portion.

8. The combination set forth in claim 7 wherein the means for effecting movement of said rotatable member comprises a pinion supported in said housing and engaging the toothed peripheral portion of said rotatable memher.

9. The combination set forth in claim 6 wherein said second resistor subtends an angle of less than 180, and wherein said rotatable member is supported for rotation about said fixed member, the concentric portion of said groove in the rotatable member subtending an angle of substantially 180 and the eccentric portion of said groove, likewise, subtending an angle of 180.

10. A double potentiometer assembly comprising, a housing, an operating shaft rotatably supported in said housing, a fixed resistor base supported in said housing and having an arcuate groove concentric with said shaft, a movable resistor base supported for rotation about said fixed resistor base and having a groove which subtends an angle of 360", one portion of the groove in said mov able resistor base being eccentric with respect to said shaft and another portion of said groove being concentric with said shaft, a first wire wound resistor fixedly supported in the groove of said fixed resistor base, a second wire wound resistor, means attached to said second resistor having portions disposed in the groove of said movable resistor base, wiper means attached to and rotatable with said shaft for contacting said resistors, and means for rotating said movable resistor base so as to vary the configuration of said second resistor to match the resistance characteristics thereof with the resistance characteristics of said first resistor.

No references cited. 

